1. Field of the Invention
The invention relates to the modification of polyols by the addition of epoxy resin and, more particularly, relates to the addition of epoxy resin to low functionality polyols at places other than the end of the polyol chain to produce a modified polyol in the 200-1000 molecular weight range suitable for use in improved rigid polyisocyanurate foam formulations.
2. Description of the Prior Art
Presently, polyether polyols suitable for use in rigid isocyanurate foams are made by the reaction of diols or triols with 1,2-alkylene oxides. Persons skilled in the art of making polyols can add alkylene oxides to polyhydric initiators such as glycerine, ethylene glycol, diethylene glycol, etc. to prepare products in the 125-1000 hydroxyl number range. While generally satisfactory, foam prepared from these prior art polyols have poor compressive strengths and poor dimensional stability. Therefore, it is an object of this invention to increase the functionality of low molecular weight diols or triols by their reaction with epoxy resins to prepare a new type of polyether polyol which would produce improved rigid polyisocyanurate foams.
Other patents disclose reactions involving polyols and epoxy resins. Japanese Patent No. 71-24,255 concerns the reaction of an alkylene glycerine based 3,000 molecular weight triol with 2% bisphenol A epoxy resin to produce foams with increased hardness. A close examination of this patent will show that the epoxy resin is added only at the end of the polyol chain. Our invention involves the addition of diols to polyepoxides so that the epoxy resin derivative is in the interior of the polyol. The preparation of our products is more easily accomplished and is more reproducible.
U.S. Pat. No. 3,012,984 describes how hydroxyl terminated polyesters, epoxy resins and isocyanate terminated prepolymers may be reacted in an inert organic solvent to produce metal primers and coatings. U.S. Pat. No. 3,010,940 discloses how phenol, epoxy resins, polyisocyanates and alpha-methylbenzyldimethylamine react to produce various polyurethane coatings. U.S. Pat. No. 3,448,046 describes how polyols containing chlorine are mixed with epoxy resins before reaction with an isocyanate. The free epoxides scavenge the HCl in the polyol and do not contribute to the functionality of the resulting polyol. The reaction of an epoxide with an alcoholic hydroxyl groups is set out in U.S. Pat. No. 3,317,609. Further, British Pat. No. 968,102 describes how polyols suitable for polyurethane foams may be prepared from the reaction of a polyol, and an epoxy resin in the presence of an acidic catalyst.
Further prior art polyols include those described in German Offenlegungschrifft No. 2,056,080. This patent describes how epoxy adhesives may be made by the reaction of epoxy resins with 4-mercaptobutanol-blocked urethane prepolymers which are made from toluene diisocyanate and various polyols. German Offenlegungschrifft No. 1,905,696 discloses how polyurethane lattices may be produced by chain-extending a urethane prepolymer by using the reaction product of polyethylene glycols of a molecular weight of about 5,000 to 10,000, and an aromatic diglycidyl ether. The modification of epoxy resins by heating them with added polyalkoxylated disaccharides is described in Belgium Pat. No. 785,020.